Rail car movers are used to maneuver rail cars around yards, plants, and like industrial sites. Such rail car movers vary considerably in size, complexity, and cost depending on the number and weight of rail cars being moved, maneuverability required, and so forth.
Some rail car movers are manufactured specifically for the purpose, and are capable of moving several loaded cars, however they are costly and often provide significantly more motive performance than is required. Such rail car movers are disclosed in U.S. Pat. Nos. 4,497,257 and 4,537,137 to White, Jr., and U.S. Pat. No. 4,843,973 to Hartelius et al. Typically these have rail wheel sets and road wheel sets configured such that one set is entirely raised out of contact so that the other set can rest on either the road or rail and bear the load. These rail car movers include driven rail wheels and driven road wheels. Whichever wheels are in use are driven by the engine of the mover.
Such rail car movers can gain traction by transferring weight from the rail car to the mover, essentially by lifting up on the rail car coupler and thereby creating a downward force on the mover wheels on the track. Such a system is generally disclosed for example in U.S. Pat. No. 3,884,156 to Ames et al.
More economical alternatives are also known wherein conventional tractors or the like are converted into rail car movers. While motive performance is reduced, these can provide satisfactory performance in many situations, and cost much less. U.S. Pat. No. 4,266,483 to Rannanmaki discloses a modified tractor where the conventional pneumatic rear wheels and tires are replaced by a flanged wheel for engaging the track. A rear axle with pneumatic road wheels is added behind the flanged wheels, and moves up and down in response to hydraulic cylinders operated with the tractors hydraulic power supply. In the road mode, the pneumatic road wheels are driven by the power take off of the tractor. A front rail axle with rail wheels is also added ahead of the conventional front axle, and similarly moves up and down as required. A coupler is located at the rear end of the tractor for attachment of a rail car.
Similarly U.S. Pat. No. 6,199,485 to Pyle discloses a rail conversion module for a tractor. A rear module has rail wheels attached and pivots up and down. The rail wheels in this apparatus are driven by the power take off of the tractor. Front rail wheels are pivotally attached behind the front road wheels. A coupler is located at the rear end of the rear module for attachment of a rail car.
While the above use driven rail wheels for propulsion, it is also known to leave some weight on the vehicle's conventional pneumatic tires in rail mode, thereby allowing the vehicle to be propelled by the tires conventionally while being guided down the rails by the rail wheels. Such road/rail vehicles are generally disclosed in U.S. Pat. No. 3,980,025 to Olson, Sr. et al. and U.S. Pat. No. 5,156,639 to Bostrum. These vehicles are not used as rail car movers however, but rather as road/rail transport or maintenance vehicles.
It is not uncommon for rail car movers to sit idle for significant periods of time. At grain terminal sites for example, several days may pass between trains. The rail car mover is used moving cars as the train is loaded, and then is not required until the next train arrives. Other industrial sites have similar use cycles for rail car movers.
The rail car movers of Rannanmaki and Pyle do allow relatively economical conversion of a conventional vehicle, a tractor, into a rail car mover, however the modifications required are significant, and do not lend themselves to quick conversion to another purpose such as conventional use of the tractor on the ground. As a result, these rail car movers converted from tractors often spend more time idle than working.